Locking bone plate

ABSTRACT

A bone plate with a longitudinal axis has a bone-contacting bottom side and a top side. Sets of overlapping holes communicate through the plate from the top to the bottom side. The overlapping holes have multifaceted surfaces such as a threaded surface or a coaxial series of annular grooves. The sets of overlapping holes are a adapted to receive a bone screw with a head and a bone-engaging thread.

BACKGROUND OF THE INVENTION

This invention relates to devices, implants and prostheses used inorthopedic surgery, and, more particularly, to bone plates used toreinforce fractured bones and thus promote healing.

A compressive screw system, also known as the DCS system, is a boneplate system that has been used in trauma surgery for many years. Theprocedures for use of this system are well documented by the AOInstitute, an institute having as one of its goals, the promotion of neworthopaedic surgical procedures. This system included a bone platehaving slots communicating therethrough A land in which the slot iswider at one end defines a stepped surface adjacent the portion of theslot that extends through the bone plate. The stepped surface isgenerally cut with a spherical endmill, thus creating a sphericalstepped surface.

In a still further development, bone plates have been developed havingindividual threaded apertures and non-threaded apertures interspersedalong the length of the plate. In this and other designs, the distancebetween holes has become a standard. Although an improvement over theinserts noted above, the locking positions are pre-defined, and onlyavailable in limited locations, which also reduce surgical flexibility.In another product variation, expandable, lockable inserts enter intothe slots of a standard bone plate. When the bone screw passes throughone of these inserts and is torqued down, the insert expands and locksthe screw in place. However, this insert is locked in a secondaryoperation. This is not desirable because this requires more operatingroom tine and adds complexity to the procedure. Further, the insertsmust be added in the specific location before the plate is fixed to thebone and cannot be subsequently inserted. This limits the choice ofplacement during surgery if the need arises.

Also, the above insert design relies on a friction lock via contactbetween two surfaces. Friction locks are not reliable and come lose moreeasily than threaded locked holes. The result of such a design isinferior to that of the threaded plate and screw designs discussedbelow.

In U.S. Pat. No. 5,002,544 to Klaue et al, there is shown anosteosynthetic pressure plate having a cross-section transverse to thelongitudinal axis of the plate at at least one point being wider towardthe upper surface than toward the lower surface and the plate havingrecesses in the lower surface so that upon application to a bone thereis space between the bone and the plate. The cross-section between thescrew holes is reduced, preferably to the extent that the resistance ofthe plate to bending in this area is less than in the area of the holes.Because of the reduced bend resistance between the holes, the plate canmore easily be adapted to conform to the anatomy of the bone.Furthermore, this can be done without deformation of the holes, thusminimizing the resulting loss of fatigue strength and minimizing themisfit of the screw heads.

Further, U.S. Pat. No. 5,709,686 to Takos et al describes a bone platethat has recesses or reduced thickness portions on its sides, betweenthreaded apertures. Although the purpose is not specifically described,these recesses appear to function to avoid warpage of the threadedportions when the bone plate is bent. However, when such a bone plate isfixed to a bone, these discontinuous recesses are exposed and maypotentially come into contact with and potentially aggrevate muscletissue.

Still further, U.S. Pat. No. 5,733,287 to Tepic et al shows (in FIG. 4),a plate that has transverse cuts 13 and a longitudinal cut 14 on thelower surface 7 to reduce contact between the plate and bone. Due to thetransverse undercuts 13, the cross-section 15 between the holes isalready significantly reduced and therefore is not further decreased byan additional groove 10 on the upper surface 6 as in the embodimentaccording to FIG. 3. To avoid a cross-section that is too thin, thegroove 10 on the upper surface 6 is made discontinuous in shortsegmental grooves 16 providing a smooth transition into and out of theholes 8.

In yet another solution, PCT application no. WO01/54601 combines thefeatures of the DCS system discussed above with a locking screw. Thisdesign combines the features of the DCS system with a locking screw.Such a system is known as the combi-slot In this design, the steppedsurface of the slot is generally ramped or tapered so as to be deeper atone end than at another. This enables the positioning and selectivefixing of the bone plate for compressing two bone fragments togetherwith a preload created by wedging action. In this manner, the bones areplaced in a position that the surgeon believes would best promotehealing.

Further, this combi-hole includes two distinct overlapping portions in asingle slot. One portion of the slot is suited to receive a standardbone screw, while the other portion of the slot is suited to receive athreaded peg oriented perpendicular to the top surface of the boneplate. Also, the combi-holes are generally oriented with the threadedportions being on the innermost end of the combination and theunthreaded portions oriented toward the ends of the bone plate. Thisimprovement increased the flexibility of choice available to orthopaedicsurgeons using the device in that it was more likely that a hole wouldbe present at a suitable anchoring point in the bone plate.Nevertheless, there are often trauma situations that are best served bythe threaded portion being at the extreme ends of the bone plate and/orat various positions throughout the plate. In addition, sometimes thereis no specific center of the facture—in such a situation, use of thecombi-hole design is limited.

While patent application no. WO01/54601 has proven advantageous becausescrews can be locked to the plate, the presence of an unthreaded slotlimits the users ability to have multiple orientations for the screw.

In a further development, the AO Institute has studied and proposed theuse of endpegs which are rigidly fixed in the extreme ends of the boneplate. Such an arrangement has been shown to better resist the flexingof the bone than use of a bone screw alone. Flexing can otherwise loosenthe connection between the bone plate and bone in other bone platesystems.

In another development, German patent DE 4341980 A1, published on Jun.14, 1995, describes a bone plate 2 having an elongated slot 8 in whichthe sidewalls of the long sides of the slot are not parallel and arefurther provided with an internal thread 9. Corresponding bone screws 3or inserts 6 have a head 5 with an external taper 4 and thus can befixed into any point along the length, but to various depths ofpenetration. Therefore, the final configuration upon fixing isindeterminate and, due to the small amount of contact between thethreads of the insert or screw and the slot, as well as the fact thatthe screw will be able to slide in one direction, the design does notappear to lend itself to reliable fixing.

U.S. Pat. No. 5,324,290 shows a complex bone plate having slots withcountersunk circular recessed cut at intervals along the slot (a similararrangement is shown in U.S. Pat. No. 4,696,290). It further shows thebone plate torqued against the bone so as to at least marginally,conform to the shape of the bone (see FIG. 2). Other patents of interestinclude U.S. Pat. Nos. 3,716,050, 3,659,595, 5,681,311, 5,261,910, and5,364,399, all showing combinations of conventional slots and recesseswhich do not fully accommodate a bone screw having a threaded head.

In comparison with the combi-hole design and the friction locking designdescribed above, what is needed is a bone plate that provides greaterflexibility of choice to the surgeon. More specifically, what is neededis a bone plate that provides this choice of plate placement whilereliably and permanently fixing the bone plate to the bone fragments, inany hole position.

What is needed is a bone plate that provides greater flexibility ofchoice to the surgeon, in a bone plate that has multiple orientationsfor the locking screw and thus, plate placement, while reliably andpermanently fixing the bone plate to the bone fragments, in any holeposition.

In addition, what is needed is a versatile bone plate having recesseswhich determine where the bone plate will bend, in order to avoid thethreads in any holes to be bent or warped, while maintaining a smoothexternal surface.

Finally, what is needed is a bone plate with holes that createbi-directional compression.

SUMMARY OF THE INVENTION

A bone plate is provided having a longitudinal axis, a bone-contactingbottom side and a top side. Sets of overlapping holes communicatethrough the plate from the top to the bottom side. The overlapping holeshave multifaceted surfaces such as a threaded surface or a coaxialseries of annular grooves. The sets of overlapping holes are adapted toreceive a bone screw with a head and a bone-engaging thread

An object of the invention is to provide an orthopaedic surgeon greaterflexibity of choice in that a threaded peg providing secure fixing canbe positioned at any interval along the bone plate, including at itsextreme ends.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a perspective view of a bone plate in which the overlappingholes align along a longitudinal axis of the bone plate.

FIG. 1 b is a top plan view of a bone plate in which the overlappingholes align along a longitudinal axis of the bone plate.

FIG. 1 c is a longitudinal cross-sectional view of a bone plate in whichthe overlapping holes align along a longitudinal axis of the bone plate.

FIG. 1 d is a top plan view of a single set of overlapping holes.

FIG. 2 a is a perspective view of a set of two overlapping holes havinga threaded surface.

FIG. 2 b is a perspective view of a set of two overlapping holes inwhich the surface of each hole is a coaxial series of annular grooves.

FIG. 3 is a longitudinal cross-section view in which some of theoverlapping holes are formed normal to the top side of the plate.

FIG. 4 is a longitudinal cross-sectional view in which all theoverlapping holes are formed at an angle offset from normal to the topside of the plate.

FIG. 5 is a top plan view of a bone plate in which the overlapping holesare staggered along a longitudinal axis of the bone plate.

FIG. 6 a is a top plan view of the bone plate showing a set of threeoverlapping holes.

FIG. 6 b is a longitudinal cross-sectional view showing the sets of treeoverlapping holes in which all holes are aligned normal to the topsurface of the bone plate.

FIG. 6 c is a longitudinal cross-sectional view showing the sets of treeoverlapping holes in which some of the holes are aligned normal to thetop surface of the bone plate.

FIG. 6 d is a longitudinal cross-sectional view showing the sets of treeoverlapping holes in which all holes are aligned at an angle offset fromnormal to the top surface of the bone plate.

FIG. 7 a is a plan view of an orthopaedic kit of the invention includinga case, a bone plate, a variety of bone screws, and threaded pegs ofvarious lengths.

FIG. 7 b is a perspective view of an orthopaedic kit of the inventionincluding a case, a bone plate, a variety of bone screws, and a drillguide.

FIG. 8 is a side view of a bone screw having a head and a bone-engagingthread.

FIG. 9 a is a perspective view of an alternate embodiment of the boneplate having lower recesses.

FIG. 9 b is a second perspective view of the alternate embodiment of thebone plate.

FIG. 9 c is a side view of the alternate embodiment of the bone plate.

FIG. 10 a is a perspective view of a second alternate embodiment showinglower recesses on the bone plate.

FIG. 10 b is a bottom view of the alternate embodiment of the boneplate.

FIG. 10 c is a side view of the alternate embodiment of the bone plate.

DETAILED DESCRPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 a to 1 d, a bone plate 10 with a longitudinalaxis 12 has a bone-contacting bottom side 14 and a top side 16. Multiplesets 20 of overlapping holes 22 communicate through the plate 10 fromthe top side 16 to the bottom side 14. The overlapping holes 22 areadapted to receive a bone screw 24 with a head 26 having a thread 30and, on an opposite end 32, a body having a bone-engaging thread 34(shown in FIG. 8).

The multiple sets 20 of overlapping holes 22 allow for furtheradjustability and flexibility in positioning of the bone plate 10 duringsurgery. The overlapping holes 22 are formed normal to the top side 16of the plate 10 (shown in FIGS. 1 c and 1 d).

Referring now to FIGS. 2 a and 2 b, the overlapping holes 22 havemultifaceted surfaces 36. In one embodiment, the multifaceted surface 36is a threaded surface 40 (shown in FIG. 2 a). In another embodiment, themulti-faceted surface 36 is a coaxial series of annular grooves 42(shown in FIG. 2 b).

Overlapping holes 22 are formed individually at an angle Ø offset fromnormal to the top side 16 of the plate 10. Such allows furtherflexibility of choice to the surgeon as to where and how to fasten thebone plate 10. Referring again to FIGS. 1 c and 1 d, where theseoverlapping holes 22 are oriented perpendicular to the top side 16 ofthe bone plate 10, he may chose to fasten the plates in a conventionalmanner, namely, perpendicular to the top side of the plate.

Referring now to FIG. 3, in a preferred embodiment, some of theoverlapping holes 22 are formed normal to the top side 16 of the plate10.

Alternatively, as shown in FIG. 4, all of the overlapping holes 22 areformed at an angle Ø offset from normal to the top side 16 of the plate10.

Referring now to FIG. 5, the overlapping holes 22 may be formed offsetfrom the longitudinal axis 12 of the bone plate 10, in a staggeredmanner.

Referring now to FIGS. 6 a to 6 d, in an alternate embodiment, the boneplate 10 may include sets 20 of three overlapping holes 22. Referring inparticular to FIGS. 6 b, where these overlapping holes 22 are orientedperpendicularly to the top side 16 of the bone plate 10, the surgeon maychose to fasten the plates in a conventional manner.

Referring in particular to FIG. 6 c, in a preferred embodiment, some ofthe overlapping holes 22 are formed normal to the top side 16 of theplate 10.

Alternatively, as shown in FIG. 6 d, all of the overlapping holes 22 areformed at an angle Ø off set from normal to the top side 16 of the plate10.

Referring now to FIGS. 7 a and 7 b, in another embodiment, orthopaedickits 44 are provided which include a case 46, a bone plate 10, a varietyof bone screws 24, threaded pegs 50 of various lengths, and a drillguide 52. The drill guide 52 has a threaded end 54 that threads into thethread 40 of an overlapping hole 22. The drill guide 52 has a main drillguide surface 56 to securely hold the drill guide in a desiredorientation with respect to the bone plate 10 in order to stabilize adrill (not shown) used in an orthopaedic procedure.

Referring now to FIGS. 9 a -9 c, an alternate embodiment of the boneplate 10′ is provided with lower recesses 60 of rectangular form,extending transversely across the bone plate. These recesses 60 arepreferably positioned at regular intervals along the longitudinal axis,between threaded apertures 62. Such recesses 60 are provided in order toreduce the contact area between the bottom side 14 of the bone plate 10′and the bone, as well as to prevent bending of the bone plate across athreaded aperture 62 (thus preventing warping of the threads 36). Thetotal area removed from the bottom side 14 due to the recesses 60 ispreferably less than or equal to 25% of the total surface area of thebottom side.

The recesses 60 are substantially located exclusively on the bottom side14 and are sized so as to define a cross-section 64 transverse to thelongitudinal axis and across the recesses. This ensures that a yieldstrength in bending across the recesses 60 is less than across athreaded aperture 62 and thus, prevents damage of the threads uponforming of the bone plate to mate with a curvilinear surface of a bone.

Referring now to FIGS. 10 a-10 c, a second alternate embodiment of thebone plate 10″ is shown having another form of lower recesses 66. Theserecesses 66 do not extend across the bottom side 14 of the bone plate10″, but rather extend from a side 70 of the bone plate a short distancetoward the centerline 12 of the bone plate, but do not traverse thecenterline.

Note that the threaded apertures 100 used in the invention provide holecenters located at specific locations (as opposed to apertures that areformed as a slot). Use of threads centered at a specific point allowsthe bone screw to be fixed at a specific location at which the surgeonmay judge the bone structure to be best suited to support such a bonescrew. Unlike designs using a slot, the apertures 100 of the inventioneliminate wander of the screw in the aperture. This further permitsplacement at specific locations for buttressing and/or secure fixing inneutral screw loading areas.

In another feature, locking bone pegs (not shown) interface with thethreaded apertures The threads cut in the head of these pegs aredesigned so as to lock with the threaded apertures in order to betterensure rigid fixing of a fixture when using pegs having a body withoutthreads. The locking feature used can be any of the known methods oflocking threads by mechanical means.

In an advantage of the invention, the bone plate 10 provides greaterflexibility of choice to the surgeon in that a threaded peg providingsecure fixing can be positioned at any interval along the bone plate,including at its extreme ends.

In another advantage, the bone plate 10 provides greater flexibility ofchoice by providing multiple overlapping holes 22 oriented (1) along thelongitudinal axis 12 of the bone plate, (2) oriented at an angle Ø tothe longitudinal axis, and (3) staggered along the axis.

In still another advantage, the threaded apertures 40 of the bone plate10 are provided with threads cut perpendicular to the top side 16 of thebone plate, as well as at an angle Ø to normal.

Multiple variations and modifications are possible in the embodiments ofthe invention described here. Although certain illustrative embodimentsof the invention have been shown and described here, a wide range ofmodifications, changes, and substitutions is contemplated in theforegoing disclosure. In some instances, some features of the presentinvention may be employed without a corresponding use of the otherfeatures. Accordingly, it is appropriate that the foregoing descriptionbe construed broadly and understood as being given by way ofillustration and example only, the spirit and scope of the inventionbeing limited only by the appended claims.

1. A bone plate with a longitudinal axis, a bone-contacting bottom sideand a top side with at least one set of overlapping holes whichcommunicate through the plate from the top to the bottom side, whereinthe at least one set of overlapping holes defines a threaded aperturehaving multifaceted surface.
 2. The bone plate of claim 1, wherein theoverlapping holes are formed normal to the top side of the plat.
 3. Thebone plate of claim 1, wherein the overlapping holes are formed at anangle offset from normal to the top side of the plate.
 4. The bone plateof claim 1, wherein at least one of the overlapping holes is formednormal to the top side of the plate and at least a second of theoverlapping holes is formed at an angle offset from normal to the topside of the plate.
 5. The bone plate of claim 1, wherein themulti-faceted surface is a coaxial series of annular grooves.
 6. Thebone plate of claims 1, wherein the threaded aperture further comprisesmultiple sets of overlapping holes.
 7. The bone plate of claim 6,wherein the overlapping holes are formed normal to the top side of theplate.
 8. The bone plate of claim 6, wherein the overlapping holes areformed at an angle offset from normal to the top side of the plate. 9.The bone plate of claim 6, wherein at least one of the overlapping holesis formed normal to the top side of the plate and at least a second ofthe overlapping holes is formed at an angle offset from normal to thetop side of the plate.
 10. The bone plate of claim 6, wherein themultiple sets of overlapping holes are aligned on the axis.
 11. The boneplate of claim 6, wherein the multiple sets of overlapping holes arepositioned in a staggered arrangement from the longitudinal axis. 12.The bone plate of claim 11, wherein the overlapping holes are formednormal to the top side of the plate.
 13. The bone plate of claim 11,wherein the overlapping holes are formed at an angle offset from normalto the top side of the plate.
 14. The bone plate of claim 11, wherein atleast one of the overlapping holes is formed normal to the top side ofthe plate and at least a second of the overlapping holes is formed at anangle offset from normal to the top side of the plate.
 15. The boneplate of claim 1, wherein the multi-faceted surface is a threadedsurface.
 16. The bone plate of claim 15, wherein the overlapping holesare formed normal to the top side of the plate.
 17. The bone plate ofclaim 15, wherein the overlapping holes are formed at an angle offsetfrom normal to the top side of the plate.
 18. The bone plate of claim15, wherein at least one of the overlapping holes is formed normal tothe top side of the plate and at least a second of the overlapping holesis formed at an angle offset from normal to the top side of the plate.19. The bone plate of claim 1 wherein the set of overlapping holes isadapted to receive a bone screw with a head and a bone-engaging thread.20. The bone plate of claim 19, wherein the head of the bone screw has aplate engaging thread.
 21. The bone plate of claim 19, wherein theoverlapping holes are formed normal to the top side of the plate. 22.The bone plate of claim 19, wherein the overlapping holes are formed atan angle offset from normal to the top side of the plate.
 23. The boneplate of claim 19, wherein at least one of the overlapping holes isformed normal to the top side of the plate and at least a second of theoverlapping holes is formed at an angle offset from normal to the topside of the plate.
 24. The bone plate of claim 1 wherein the set iscomprised of two overlapping holes.
 25. The bone plate of claim 24,wherein the overlapping holes are formed normal to the top side of theplate.
 26. The bone plate of claim 24, wherein the overlapping holes areformed at an angle offset from normal to the top side of the plate. 27.The bone plate of claim 24, wherein at least one of the overlappingholes is formed normal to the top side of the plate and at least asecond of the overlapping holes is formed at an angle offset from normalto the top side of the plate.
 28. The bone plate of claim 1, wherein theset is comprised of three overlapping holes.
 29. The bone plate of claim28, wherein the overlapping holes are formed normal to the top side ofthe plate.
 30. The bone plate of claim 28, wherein the overlapping holesare formed at an angle offset from normal to the top side of the plate.31. The bone plate of claim 28, wherein at least one of the overlappingholes is formed normal to the top side of the plate and at least asecond of the overlapping holes is formed at an angle offset from normalto the top side of the plate.
 32. An orthopaedic kit including: a. abone plate with a longitudinal axis, a bone-contacting bottom side and atop side with at least one set of overlapping holes which communicatethrough the plate from the top to the bottom side, the overlapping holesdefining a threaded aperture having multifaceted surfaces; and b. atleast one bone screw engageable with the bone plate.
 33. The kit ofclaim 32, further comprising a drill guide having a main drill guidesurface and opposite end portions, one end portion of which is securelyengageable with the multi-faceted surface of a hole in the bone plate soas to securely hold the drill guide in a desired orientation withrespect to the bone plate for stabilizing a drill used in an orthopaedicprocedure.
 34. A bone plate with a longitudinal axis, a bone-contactingbottom side and a top side with a plurality of sets of overlapping holeswhich communicate through the plate from the top to the bottom side,wherein the set of overlapping holes have threads adapted to receive abone screw with a threaded head and a bone engaging threaded shank. 35.A bone plate with a longitudinal axis, a bone-contacting bottom side anda top side with a plurality of sets of overlapping holes whichcommunicate through the plate from the top to the bottom side, theoverlapping holes having threaded success adapted to receive bone screwswith a threaded head and a bone engaging thread shank, wherein theoverlapping holes have centers substantially aligned along thelongitudinal axis of the plate.
 36. A bone plate with a longitudinalaxis, a bone-contacting bottom side and a top side with a plurality ofthreaded apertures communicating through the plate from the top to thebottom side, at least one of the threaded apertures comprised ofoverlapping holes having a threaded surface adapted to receive a bonescrew with a head and a bone engaging thread, the overlapping holesfurther having centers staggered about the longitudinal axis of theplate.
 37. A bone plate with a longitudinal axis, a bone-contactingbottom side having a total area and a top side with a plurality ofthreaded apertures which communicate through the plate from the top sideto the bottom side, at least one of which is a set of overlapping holes,wherein the overlapping holes have multifaceted surfaces and wherein thebottom side includes recesses located between adjacent threadedapertures and which are substantially located exclusively on the bottomside, the recesses being sized so as to define a cross-sectiontransverse to the longitudinal axis and across the recesses that ensuresthat a yield strength in bending across the recesses is less than acrossa threaded aperture.
 38. The bone plate of claim 37, wherein therecesses are substantially rectangular in form.
 39. The bone plate ofclaim 37, wherein the recesses are equally spaced along the longitudinalaxis.
 40. The bone plate of claim 37,wherein the total area removed fromthe bottom side due to the recesses is less than or equal to 50% of thetotal surface area of the bottom side.
 41. The bone plate of claim 37,wherein the recesses are transverse and extend across the width of thebone plate.
 42. The bone plate of claim 37, wherein the recesses extendfrom a side of the bone plate transversely toward the longitudinal axisbut do not cross the axis.